# Copyright 2015 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Fully connected RNN layer."""


import tensorflow.compat.v2 as tf

from keras import activations
from keras import backend
from keras import constraints
from keras import initializers
from keras import regularizers
from keras.engine import base_layer
from keras.engine.input_spec import InputSpec
from keras.layers.rnn import rnn_utils
from keras.layers.rnn.base_rnn import RNN
from keras.layers.rnn.dropout_rnn_cell_mixin import DropoutRNNCellMixin
from keras.utils import tf_utils

# isort: off
from tensorflow.python.platform import tf_logging as logging
from tensorflow.python.util.tf_export import keras_export


@keras_export("keras.layers.SimpleRNNCell")
class SimpleRNNCell(DropoutRNNCellMixin, base_layer.BaseRandomLayer):
    """Cell class for SimpleRNN.

    See [the Keras RNN API guide](https://www.tensorflow.org/guide/keras/rnn)
    for details about the usage of RNN API.

    This class processes one step within the whole time sequence input, whereas
    `tf.keras.layer.SimpleRNN` processes the whole sequence.

    Args:
      units: Positive integer, dimensionality of the output space.
      activation: Activation function to use.
        Default: hyperbolic tangent (`tanh`).
        If you pass `None`, no activation is applied
        (ie. "linear" activation: `a(x) = x`).
      use_bias: Boolean, (default `True`), whether the layer uses a bias vector.
      kernel_initializer: Initializer for the `kernel` weights matrix,
        used for the linear transformation of the inputs. Default:
        `glorot_uniform`.
      recurrent_initializer: Initializer for the `recurrent_kernel`
        weights matrix, used for the linear transformation of the recurrent
        state.  Default: `orthogonal`.
      bias_initializer: Initializer for the bias vector. Default: `zeros`.
      kernel_regularizer: Regularizer function applied to the `kernel` weights
        matrix. Default: `None`.
      recurrent_regularizer: Regularizer function applied to the
        `recurrent_kernel` weights matrix. Default: `None`.
      bias_regularizer: Regularizer function applied to the bias vector.
        Default: `None`.
      kernel_constraint: Constraint function applied to the `kernel` weights
        matrix. Default: `None`.
      recurrent_constraint: Constraint function applied to the
        `recurrent_kernel` weights matrix. Default: `None`.
      bias_constraint: Constraint function applied to the bias vector. Default:
        `None`.
      dropout: Float between 0 and 1. Fraction of the units to drop for the
        linear transformation of the inputs. Default: 0.
      recurrent_dropout: Float between 0 and 1. Fraction of the units to drop
        for the linear transformation of the recurrent state. Default: 0.

    Call arguments:
      inputs: A 2D tensor, with shape of `[batch, feature]`.
      states: A 2D tensor with shape of `[batch, units]`, which is the state
        from the previous time step. For timestep 0, the initial state provided
        by user will be feed to cell.
      training: Python boolean indicating whether the layer should behave in
        training mode or in inference mode. Only relevant when `dropout` or
        `recurrent_dropout` is used.

    Examples:

    ```python
    inputs = np.random.random([32, 10, 8]).astype(np.float32)
    rnn = tf.keras.layers.RNN(tf.keras.layers.SimpleRNNCell(4))

    output = rnn(inputs)  # The output has shape `[32, 4]`.

    rnn = tf.keras.layers.RNN(
        tf.keras.layers.SimpleRNNCell(4),
        return_sequences=True,
        return_state=True)

    # whole_sequence_output has shape `[32, 10, 4]`.
    # final_state has shape `[32, 4]`.
    whole_sequence_output, final_state = rnn(inputs)
    ```
    """

    def __init__(
        self,
        units,
        activation="tanh",
        use_bias=True,
        kernel_initializer="glorot_uniform",
        recurrent_initializer="orthogonal",
        bias_initializer="zeros",
        kernel_regularizer=None,
        recurrent_regularizer=None,
        bias_regularizer=None,
        kernel_constraint=None,
        recurrent_constraint=None,
        bias_constraint=None,
        dropout=0.0,
        recurrent_dropout=0.0,
        **kwargs,
    ):
        if units < 0:
            raise ValueError(
                "Received an invalid value for argument `units`, "
                f"expected a positive integer, got {units}."
            )
        # By default use cached variable under v2 mode, see b/143699808.
        if tf.compat.v1.executing_eagerly_outside_functions():
            self._enable_caching_device = kwargs.pop(
                "enable_caching_device", True
            )
        else:
            self._enable_caching_device = kwargs.pop(
                "enable_caching_device", False
            )
        super().__init__(**kwargs)
        self.units = units
        self.activation = activations.get(activation)
        self.use_bias = use_bias

        self.kernel_initializer = initializers.get(kernel_initializer)
        self.recurrent_initializer = initializers.get(recurrent_initializer)
        self.bias_initializer = initializers.get(bias_initializer)

        self.kernel_regularizer = regularizers.get(kernel_regularizer)
        self.recurrent_regularizer = regularizers.get(recurrent_regularizer)
        self.bias_regularizer = regularizers.get(bias_regularizer)

        self.kernel_constraint = constraints.get(kernel_constraint)
        self.recurrent_constraint = constraints.get(recurrent_constraint)
        self.bias_constraint = constraints.get(bias_constraint)

        self.dropout = min(1.0, max(0.0, dropout))
        self.recurrent_dropout = min(1.0, max(0.0, recurrent_dropout))
        self.state_size = self.units
        self.output_size = self.units

    @tf_utils.shape_type_conversion
    def build(self, input_shape):
        super().build(input_shape)
        default_caching_device = rnn_utils.caching_device(self)
        self.kernel = self.add_weight(
            shape=(input_shape[-1], self.units),
            name="kernel",
            initializer=self.kernel_initializer,
            regularizer=self.kernel_regularizer,
            constraint=self.kernel_constraint,
            caching_device=default_caching_device,
        )
        self.recurrent_kernel = self.add_weight(
            shape=(self.units, self.units),
            name="recurrent_kernel",
            initializer=self.recurrent_initializer,
            regularizer=self.recurrent_regularizer,
            constraint=self.recurrent_constraint,
            caching_device=default_caching_device,
        )
        if self.use_bias:
            self.bias = self.add_weight(
                shape=(self.units,),
                name="bias",
                initializer=self.bias_initializer,
                regularizer=self.bias_regularizer,
                constraint=self.bias_constraint,
                caching_device=default_caching_device,
            )
        else:
            self.bias = None
        self.built = True

    def call(self, inputs, states, training=None):
        prev_output = states[0] if tf.nest.is_nested(states) else states
        dp_mask = self.get_dropout_mask_for_cell(inputs, training)
        rec_dp_mask = self.get_recurrent_dropout_mask_for_cell(
            prev_output, training
        )

        if dp_mask is not None:
            h = backend.dot(inputs * dp_mask, self.kernel)
        else:
            h = backend.dot(inputs, self.kernel)
        if self.bias is not None:
            h = backend.bias_add(h, self.bias)

        if rec_dp_mask is not None:
            prev_output = prev_output * rec_dp_mask
        output = h + backend.dot(prev_output, self.recurrent_kernel)
        if self.activation is not None:
            output = self.activation(output)

        new_state = [output] if tf.nest.is_nested(states) else output
        return output, new_state

    def get_initial_state(self, inputs=None, batch_size=None, dtype=None):
        return rnn_utils.generate_zero_filled_state_for_cell(
            self, inputs, batch_size, dtype
        )

    def get_config(self):
        config = {
            "units": self.units,
            "activation": activations.serialize(self.activation),
            "use_bias": self.use_bias,
            "kernel_initializer": initializers.serialize(
                self.kernel_initializer
            ),
            "recurrent_initializer": initializers.serialize(
                self.recurrent_initializer
            ),
            "bias_initializer": initializers.serialize(self.bias_initializer),
            "kernel_regularizer": regularizers.serialize(
                self.kernel_regularizer
            ),
            "recurrent_regularizer": regularizers.serialize(
                self.recurrent_regularizer
            ),
            "bias_regularizer": regularizers.serialize(self.bias_regularizer),
            "kernel_constraint": constraints.serialize(self.kernel_constraint),
            "recurrent_constraint": constraints.serialize(
                self.recurrent_constraint
            ),
            "bias_constraint": constraints.serialize(self.bias_constraint),
            "dropout": self.dropout,
            "recurrent_dropout": self.recurrent_dropout,
        }
        config.update(rnn_utils.config_for_enable_caching_device(self))
        base_config = super().get_config()
        return dict(list(base_config.items()) + list(config.items()))


@keras_export("keras.layers.SimpleRNN")
class SimpleRNN(RNN):
    """Fully-connected RNN where the output is to be fed back to input.

    See [the Keras RNN API guide](https://www.tensorflow.org/guide/keras/rnn)
    for details about the usage of RNN API.

    Args:
      units: Positive integer, dimensionality of the output space.
      activation: Activation function to use.
        Default: hyperbolic tangent (`tanh`).
        If you pass None, no activation is applied
        (ie. "linear" activation: `a(x) = x`).
      use_bias: Boolean, (default `True`), whether the layer uses a bias vector.
      kernel_initializer: Initializer for the `kernel` weights matrix,
        used for the linear transformation of the inputs. Default:
        `glorot_uniform`.
      recurrent_initializer: Initializer for the `recurrent_kernel`
        weights matrix, used for the linear transformation of the recurrent
        state.  Default: `orthogonal`.
      bias_initializer: Initializer for the bias vector. Default: `zeros`.
      kernel_regularizer: Regularizer function applied to the `kernel` weights
        matrix. Default: `None`.
      recurrent_regularizer: Regularizer function applied to the
        `recurrent_kernel` weights matrix. Default: `None`.
      bias_regularizer: Regularizer function applied to the bias vector.
        Default: `None`.
      activity_regularizer: Regularizer function applied to the output of the
        layer (its "activation"). Default: `None`.
      kernel_constraint: Constraint function applied to the `kernel` weights
        matrix. Default: `None`.
      recurrent_constraint: Constraint function applied to the
        `recurrent_kernel` weights matrix.  Default: `None`.
      bias_constraint: Constraint function applied to the bias vector. Default:
        `None`.
      dropout: Float between 0 and 1.
        Fraction of the units to drop for the linear transformation of the
        inputs. Default: 0.
      recurrent_dropout: Float between 0 and 1.
        Fraction of the units to drop for the linear transformation of the
        recurrent state. Default: 0.
      return_sequences: Boolean. Whether to return the last output
        in the output sequence, or the full sequence. Default: `False`.
      return_state: Boolean. Whether to return the last state
        in addition to the output. Default: `False`
      go_backwards: Boolean (default False).
        If True, process the input sequence backwards and return the
        reversed sequence.
      stateful: Boolean (default False). If True, the last state
        for each sample at index i in a batch will be used as initial
        state for the sample of index i in the following batch.
      unroll: Boolean (default False).
        If True, the network will be unrolled,
        else a symbolic loop will be used.
        Unrolling can speed-up a RNN,
        although it tends to be more memory-intensive.
        Unrolling is only suitable for short sequences.

    Call arguments:
      inputs: A 3D tensor, with shape `[batch, timesteps, feature]`.
      mask: Binary tensor of shape `[batch, timesteps]` indicating whether
        a given timestep should be masked. An individual `True` entry indicates
        that the corresponding timestep should be utilized, while a `False`
        entry indicates that the corresponding timestep should be ignored.
      training: Python boolean indicating whether the layer should behave in
        training mode or in inference mode. This argument is passed to the cell
        when calling it. This is only relevant if `dropout` or
        `recurrent_dropout` is used.
      initial_state: List of initial state tensors to be passed to the first
        call of the cell.

    Examples:

    ```python
    inputs = np.random.random([32, 10, 8]).astype(np.float32)
    simple_rnn = tf.keras.layers.SimpleRNN(4)

    output = simple_rnn(inputs)  # The output has shape `[32, 4]`.

    simple_rnn = tf.keras.layers.SimpleRNN(
        4, return_sequences=True, return_state=True)

    # whole_sequence_output has shape `[32, 10, 4]`.
    # final_state has shape `[32, 4]`.
    whole_sequence_output, final_state = simple_rnn(inputs)
    ```
    """

    def __init__(
        self,
        units,
        activation="tanh",
        use_bias=True,
        kernel_initializer="glorot_uniform",
        recurrent_initializer="orthogonal",
        bias_initializer="zeros",
        kernel_regularizer=None,
        recurrent_regularizer=None,
        bias_regularizer=None,
        activity_regularizer=None,
        kernel_constraint=None,
        recurrent_constraint=None,
        bias_constraint=None,
        dropout=0.0,
        recurrent_dropout=0.0,
        return_sequences=False,
        return_state=False,
        go_backwards=False,
        stateful=False,
        unroll=False,
        **kwargs,
    ):
        if "implementation" in kwargs:
            kwargs.pop("implementation")
            logging.warning(
                "The `implementation` argument "
                "in `SimpleRNN` has been deprecated. "
                "Please remove it from your layer call."
            )
        if "enable_caching_device" in kwargs:
            cell_kwargs = {
                "enable_caching_device": kwargs.pop("enable_caching_device")
            }
        else:
            cell_kwargs = {}
        cell = SimpleRNNCell(
            units,
            activation=activation,
            use_bias=use_bias,
            kernel_initializer=kernel_initializer,
            recurrent_initializer=recurrent_initializer,
            bias_initializer=bias_initializer,
            kernel_regularizer=kernel_regularizer,
            recurrent_regularizer=recurrent_regularizer,
            bias_regularizer=bias_regularizer,
            kernel_constraint=kernel_constraint,
            recurrent_constraint=recurrent_constraint,
            bias_constraint=bias_constraint,
            dropout=dropout,
            recurrent_dropout=recurrent_dropout,
            dtype=kwargs.get("dtype"),
            trainable=kwargs.get("trainable", True),
            **cell_kwargs,
        )
        super().__init__(
            cell,
            return_sequences=return_sequences,
            return_state=return_state,
            go_backwards=go_backwards,
            stateful=stateful,
            unroll=unroll,
            **kwargs,
        )
        self.activity_regularizer = regularizers.get(activity_regularizer)
        self.input_spec = [InputSpec(ndim=3)]

    def call(self, inputs, mask=None, training=None, initial_state=None):
        return super().call(
            inputs, mask=mask, training=training, initial_state=initial_state
        )

    @property
    def units(self):
        return self.cell.units

    @property
    def activation(self):
        return self.cell.activation

    @property
    def use_bias(self):
        return self.cell.use_bias

    @property
    def kernel_initializer(self):
        return self.cell.kernel_initializer

    @property
    def recurrent_initializer(self):
        return self.cell.recurrent_initializer

    @property
    def bias_initializer(self):
        return self.cell.bias_initializer

    @property
    def kernel_regularizer(self):
        return self.cell.kernel_regularizer

    @property
    def recurrent_regularizer(self):
        return self.cell.recurrent_regularizer

    @property
    def bias_regularizer(self):
        return self.cell.bias_regularizer

    @property
    def kernel_constraint(self):
        return self.cell.kernel_constraint

    @property
    def recurrent_constraint(self):
        return self.cell.recurrent_constraint

    @property
    def bias_constraint(self):
        return self.cell.bias_constraint

    @property
    def dropout(self):
        return self.cell.dropout

    @property
    def recurrent_dropout(self):
        return self.cell.recurrent_dropout

    def get_config(self):
        config = {
            "units": self.units,
            "activation": activations.serialize(self.activation),
            "use_bias": self.use_bias,
            "kernel_initializer": initializers.serialize(
                self.kernel_initializer
            ),
            "recurrent_initializer": initializers.serialize(
                self.recurrent_initializer
            ),
            "bias_initializer": initializers.serialize(self.bias_initializer),
            "kernel_regularizer": regularizers.serialize(
                self.kernel_regularizer
            ),
            "recurrent_regularizer": regularizers.serialize(
                self.recurrent_regularizer
            ),
            "bias_regularizer": regularizers.serialize(self.bias_regularizer),
            "activity_regularizer": regularizers.serialize(
                self.activity_regularizer
            ),
            "kernel_constraint": constraints.serialize(self.kernel_constraint),
            "recurrent_constraint": constraints.serialize(
                self.recurrent_constraint
            ),
            "bias_constraint": constraints.serialize(self.bias_constraint),
            "dropout": self.dropout,
            "recurrent_dropout": self.recurrent_dropout,
        }
        base_config = super().get_config()
        config.update(rnn_utils.config_for_enable_caching_device(self.cell))
        del base_config["cell"]
        return dict(list(base_config.items()) + list(config.items()))

    @classmethod
    def from_config(cls, config):
        if "implementation" in config:
            config.pop("implementation")
        return cls(**config)
